1. Field of the Invention
The present invention is directed to the field of audio amplification and more specifically to the area of control switching of amplifiers.
2. Description of the Prior Art
Recently, in vehicular audio systems, power amplification modules have been offered as optional equipment to be added to the conventional radio. Such installations, as exemplified in FIG. 1, included a power amplifier module 10 and a 17-pole double-throw switch S10 wired between the conventional radio receiver and the output speakers associated therewith. The functions of the power amplifier unit 10 were to provide an equalizer network 12 for each channel of audio signal output from the radio receiver 8 and to boost the power of that signal to each associated speaker. The function of the equalizer network 12 was to enhance certain frequencies of audio signal output from the radio 8 for each channel and was conventionally designed to highlight certain frequencies over others, depending upon the vehicle in which it was intended to be installed. This involved tuning according to the amount and placement of both accoustically absorbing material and accoustically reflecting material which make up the interior of the vehicle. The output of the equalizer network was then fed to a power amplifier 13 which in turn produced an amplified signal used to drive a single speaker through switch S10.
The switch S10, used in these prior art installations, was relatively large and expensive since the contacts thereof were required to handle audio signals and relatively high current levels without introducing noise to the system. The system was further burdensome in that a considerable amount of labor was necessary to interconnect the large number of wires between the radio and the switch, between the switch and the speakers, between the switch and the input of the amplifier module 10 and between the output of the module 10 and the switch. Cost of components, fabrication labor and installation labor were all factors which added to the cost of this option.